Deck 17: Phase Equilibrium and Solutions

Question 1

An ice skater exerts a pressure of 3.1 MPa. Calculate the change in the melting point of the ice under the skate, given that the densities of liquid water and ice are 0.998 and 0.920 g cm^-3 respectively and the enthalpy of fusion of water is +6.01 kJ mol^-1.

A) An increase of 0.22 K
B) A decrease of 0.22 K
C) An increase of 4.6 K
D) A decrease of 4.6 K

Answer 1

B

Question 2

Determine the vapour pressure of diethyl ether, C₄H₁₀O, at a temperature of 298 K, given that the normal boiling temperature is 308 K and enthalpy of vaporization is 25.9 kJ mol^-1.

A) 34.4 kPa
B) 142 kPa
C) 101 kPa
D) 72.2 kPa

Answer 2

D

Question 3

The normal boiling temperature of trichloromethane, CHCl₃, is 61°C, and the specific enthalpy of vaporization is 250 J g^-1. Determine the vapour pressure at a temperature of 298 K.

A) 63.6 kPa
B) 67.6 kPa
C) 68.5 kPa
D) 101 kPa

Answer 3

C

Question 4

The vapour pressure of pyridine, C₅H₅N, is 2.25 kPa at 25°C. Determine the normal boiling temperature of pyridine if the enthalpy of vaporization is 40.3 kJ mol^-1.

A) 1001 K
B) 2.1°C
C) 389 K
D) 166°C

Question 5

The vapour pressure of pure 1-propanol is 2792 Pa at 25°C and 11995 Pa at 50°C. Determine the enthalpy of vaporization of 1-propanol.

A) 606 J mol^-1
B) 10.1 kJ mol^-1
C) 46.7 kJ mol^-1
D) 5.62 kJ mol^-1

Question 6

The vapour pressure of pure benzene is 0.146 bar and of pure toluene is 0.185 bar at 298 K. Determine the mole fraction of toluene in an ideal liquid mixture of benzene and toluene for which the total vapour pressure is 0.160 bar at this temperature.

A) 56.1%
B) 35.9%
C) 96.7%
D) 8.75%

Question 7

The Henry's law constant for nitrogen dissolved in water at 298 K is 8.68  10⁹ Pa. Determine the mole fraction of nitrogen in water in equilibrium with air at a pressure of 1 atm and temperature of 298 K.

A) 9.10 ppm
B) 11.0 ppm
C) 8.98 ppm
D) 7.90 ppm

Question 8

What is the osmotic pressure generated at 25°C by a solution of 1.26 g of sucrose, C₁₂H₂₂O₁₁, in 250 cm³ of water?

A) 3.06 kPa
B) 36.4 kPa
C) 12.5 kPa
D) 1.05 kPa

Question 9

Determine the mass of potassium chloride, KCl, that must be added to water to create an aqueous solution of volume 25 dm³ with an osmotic pressure of 1.0 bar.

A) 120.5 g
B) 1.01 g
C) 25.0 g
D) 75.3 g

Question 10

Trichloromethane, CHCl₃, and propanone, C₃H₆O, form liquid-vapour mixtures with a maximum-boiling azeotrope. What does this imply about the nature of the interactions between the molecules in the mixture?

A) Strong interactions between molecules make it more difficult for them to escape from the liquid to the vapour phase.
B) The interactions between the molecules in the mixture are the same strength as those of the pure components.
C) Weak interactions between the molecules increase the vapour pressure.
D) It is not possible to infer anything about the nature of the interactions.

Question 11

Determine the vapour pressure of n-hexane, C₆H₁₄, at a temperature of 298 K, given that the normal boiling temperature is 342 K and enthalpy of vaporization is 30.9 kJ mol^-1.

A) 20.4 kPa
B) 504 kPa
C) 101 kPa
D) 29.4 kPa

Question 12

Determine the vapour pressure of toluene, C₇H₈, at a temperature of 350 K, given that the normal boiling temperature is 384 K and enthalpy of vaporization is 37.1 kJ mol^-1.

A) 313 kPa
B) 32.8 kPa
C) 101 kPa
D) 3.5 kPa

Question 13

Determine the vapour pressure of acetone, C₃H₆O, at a temperature of 298 K, given that the normal boiling temperature is 329 K and enthalpy of vaporization is 31.3 kJ mol^-1.

A) 30.8 kPa
B) 333 kPa
C) 101 kPa
D) 15.9 kPa

Question 14

Estimate the increase in the vapour pressure of octane, C₈H₁₈, from when the temperature is 298 K to when the temperature is 308 K. The normal boiling temperature is 329 K and enthalpy of vaporization is 31.3 kJ mol^-1.

A) 1.54 kPa
B) 2.63 kPa
C) 99.4 kPa
D) 1.09 kPa

Question 15

Estimate the change in the vapour pressure of -pinene, C₁₀H₁₆, from when the temperature is 323 K to when the temperature is 273 K. The normal boiling temperature is 430 K and enthalpy of vaporization is 45.4 kJ mol^-1.

A) An increase of 1.44 kPa
B) A decrease of 1.44 kPa
C) An increase of 1.51 kPa
D) A decrease of 1.51 kPa

Question 16

The vapour pressure of ethanol, C₂H₆O, is 7.4 kPa at 25°C. Determine the normal boiling temperature of ethanol if the enthalpy of vaporization is 42.3 kJ mol^-1.

A) 352 K
B) 242 K
C) 877 K
D) 320 K

Question 17

The vapour pressure of methanol, CH₄O, is 27.5 kPa at 308 K. Determine the normal boiling temperature of ethanol if the enthalpy of vaporization is 37.6 kJ mol^-1.

A) 365 K
B) 240 K
C) 633 K
D) 338 K

Question 18

The vapour pressure of pure cyclohexane is 12.2 kPa at 25°C and 25.1 kPa at 42°C. Determine the enthalpy of vaporization of cyclohexane.

A) 1240 J mol^-1
B) 33.1 kJ mol^-1
C) 28.6 kJ mol^-1
D) 7.78 kJ mol^-1

Question 19

The vapour pressure of pure aniline is 1314 Pa at 350 K and 13372 Pa at 400 K. Determine the enthalpy of vaporization of aniline.

A) 550 kJ mol^-1
B) 101 kJ mol^-1
C) 53.9 kJ mol^-1
D) 29.4 kJ mol^-1

Question 20

The Henry's law constant for carbon dioxide dissolved in water at 298 K is 0.163  10⁹ Pa. Determine the mole fraction of carbon dioxide in water in equilibrium with air at a pressure of 1 atm and temperature of 298 K, assuming the proportion of carbon dioxide in dry air is 0.04%.

A) 2.6 ppm
B) 25 ppm
C) 5.0 ppm
D) 12.4 ppm

Question 21

What is the osmotic pressure generated at 25°C by a solution of 2.50 g of glucose, C₆H₁₂O₆, in 500 cm³ of water at 298 K?

A) 27.8 kPa
B) 68.8 kPa
C) 34.4 kPa
D) 10.3 kPa

Question 22

Determine the mass of sodium chloride, NaCl, that must be added to water to create an aqueous solution of volume 0.50 dm³ with an osmotic pressure of 1.0 atm at 298 K.

A) 1.19 g
B) 4.09 g
C) 5.85 g
D) 8.43 g

Question 23

0.10 g of a protein is added to 250 cm³ water at 298 K and the osmotic pressure is measured as 255 Pa. Estimate the relative molecular mass of the protein.

A) 1579 g mol⁻¹
B) 3540 g mol⁻¹
C) 250.5 g mol⁻¹
D) 3884 g mol⁻¹

Question 24

0.40 g of a protein is added to 100 cm³ water at 298 K and the osmotic pressure is measured as 185 Pa. Estimate the relative molecular mass of the protein.

A) Approx 54,000 g mol⁻¹
B) Approx 32,000 g mol⁻¹
C) 15,690 g mol⁻¹
D) 22,500 g mol⁻¹

Question 25

0.25 g of a protein is added to 250 cm³ water at 298 K and the osmotic pressure is measured as 320 Pa. Estimate the relative molecular mass of the protein.

A) Approx 4,000 g mol⁻¹
B) Approx 22,000 g mol⁻¹
C) Approx 7700 g mol⁻¹
D) Approx 13,500 g mol⁻¹